Producing Tusche Wash Effects in Screenprinting using
Toner for Images and Simple Pastes as an Ink Base
A technique to produce tusche wash effects with screen printing without the use of a photographic halftone screen. Using dry copier toners on mylar and exposed to a sensitized screen, the author then uses simple water soluble pastes and paint tinting pigments to produce screen prints that are indistinguishable from lithographs.
Screen printing, which really is a form of stenciling, has been used by early civilizations; like the cave dwellers who used their hands as a negative blockout to pigments blown at the cave surface through a reed or hollow bone. The Greeks, Egyptians and Romans all used stencils in some way to repeat designs of a decorative nature. Many groups around the world developed simple stencils to apply vegetable dyes to fabric, or mass producing religious images for the faithful. Screen printing began in China about AD 221, mainly for the productions of images of the Buddha, but soon became a method of transferring designs to fabric. The Japanese took-up the processes but perfected a method of using human hair to hold the floating islands that allowed them to hold back a clear shape surrounded by a colored area. Stiff brushes or dabbers were used to force the dye or pigment through the open spaces on to the substrate. In parts of the globe, stencils were cut from parchment, oiled paper, or thin metal, depending on the materials available and the practice of the society.
It is not known when or by whom was started the practice of using fabric stretched over a frame, but silk screens were used in France by 1870 for the printing of cloth, still a major method of manufacturing printed textiles. In 1907, a limited patent was granted to Samuel Simon of Manchester, England, for the use of silk as a support for the stencil. A brush was used to force the paint through the mesh as the squeegees was still unknown. Sometime in the early Nineteen Hundreds, the squeegee was introduced and has become the main tool of the screen printing industry.
Screen printing had its impetus in the commercial sign industry as it became the media of choice to print large bold colorful advertising signs on heavy card stock. It was perfect for the short run with the stencil cut from the new shellac stencil film tissue that revolutionized the preparation of screens. In 1928 Joe Ulano replaced the shellac tissue with a superior material made from a lacquer base, allowing for an extremely accurate hand-cut stencil.
There is some confusion as to who was successful in producing the first direct photographic screens with a coating of bichromated protein. Between 1911-15, screen printers Roy Beck, Charles Peter and Edward Owens on the west coast of United States had succeeded in producing the first photographic screens. Early experiments were conducted with glue and gelatin that was sensitized with either potassium, sodium or ammonium bichromate. First the screen would be given a coating of a warm mixture of gelatin and glue to act as medium to hold the sensitizer. After it dried, the sensitizer, consisting of a thinner mixture of coating but with enough bichromate added to give it an orange tint, was applied over the base coat. This was again dried, now in the dark, and exposed to light under a positive transparency, until the exposed parts turned a bronze color. The screen was then washed in warm water until the soft parts dissolved away to reveal the image. It had been known since the days of Fox Talbot that chromic acid salts had a hardening effect on proteins when exposed to sunlight. This phenomena had been exploited in early photography and later became the basis for photo-lithography and photo-engraving.
Now there are many variations on preparing the photo stencil with the choice of capillary, direct, indirect films and directly applied emulsions. Today gelatin, glue and albumen has been replace with polyvinyl alcohol and polyvinyl acetate, or with mixtures of all of the above. The sensitizing component is diazo powder to replace the toxic bichromate salts that have been the mainstay of the process. While less sensitive to light, diazo produces sharper images and is less toxic and harmful to the environment.
From all the various methods available to the modern screen printer, it was recommended to me by commercial printers, to use the direct application of an emulsion to the screen. because it was the best technique to retain the very fine detail that dry copier toners are able to produce.
Screenprinting in the Sign Industry
Screen printing has become the accepted technique for the small and medium sign shop as it is quick to process artwork into a printing screen. Many methods can be used to put an image on the screen fabric; some more direct than others. The cut stencil can be used for simple shapes while the photographic process can handle the most complex images. The fine artist has had to adapted many of these commercial techniques to his or her aesthetic needs after examining the availability of materials.
Because screen printing can deposit a very thick layer of opaque ink on card, paper or other surface, screen printing inks have been manufactured basically for use in the sign industry. While tinted transparent bases are used to some extent, the bulk of the inks used by todays printers are opaque. Because commercial sign printers prefer a waterproof ink, the use of solvent based inks continues to be the main stay of their industry. Development of water based inks is continuing but the general attitude of the industry is that they are not acceptable because of paper buckling and greater difficulty in printing. Only environmental and health concerns will force the sign printers from their course.
Because the sign printing industry does not require an archival ink, both the binder and pigments are chosen for their cost and ability to adhere to a particular substrata, rather than for permanency. The thicker coating of ink and the opaqueness of the pigment helps to retard fading of the finished product, so these materials have become acceptable for most artists. Many different types of inks have been perfected for various endeavors such as the electronic and packaging industries. While some of these inks may have special characteristics for certain fine art projects, on the whole, artists produce prints on paper using the simpler poster inks using cellulose binders dissolved in a strong hydrocarbon solvent.
The choice of fabric, frames and squeegees have not been a hindrance to the fine artist so the general method of working has relied much on the techniques developed by the commercial industry.
My Desire to Print Fine Graduated Tints
My love of the lithographic process and the ease with which one can get delicate tints had left me cool towards screen printing. The hard edges and opaque colors did not fit into my aesthetic sense and I avoided the process. My fine art printing continued to exploit the lithographic process and I developed a number of techniques to make the kind of image I wanted.
In 1985 I developed the lithographic toner tusche technique which gave me the textured washed that I preferred (LEONARDO, Vol. 20, #1,1987), at the same time allowing me unlimited changes on plate or stone to the unfinished image. In dry copier toner I found a material that could be used in a number techniques because of its greaseless quality and opaqueness of the individual particles of powder. The black powder, as well as the colored material, could also be used on mylar to produce images with positive lithographic plates and processed with the manufactures gum-etch, or with my waterless lithographic technique. In 1987 I had also developed, with the help of a masters student, a method of producing toner wash effect on presensitized intaglio plates. The use of dry copier toner to produce tusche wash tints with screen printing actually seemed possible.
In the summer of 1988 I did some research with toners on clear mylar using Star #71 emulsion, sensitized with ammonium bichromate. By using fine yellow monofilament fabric (245 TPI) and a very short exposure, I was able to retain the fine detail needed to produce washes. My exposures were in the range of 25-30% of normal, which required a cautious method of washing out the screen. By directing a gentle stream of cold water just on the frame, from the emulsion side, and allowing it to run down, the water would slough off only the unexposed material to reveal the image. Care was taken not to direct the stream directly on the remaining emulsion as it would be quickly washed away.
After partially drying the screen, I would spray a 10% solution of ammonium bichromate on the emulsion to replace the sensitizer that had been removed when developing the image. After drying, the screen was given another exposure without the mylar, to harden the remaining emulsion. The screen was washed again to remove the yellow sensitizer from the emulsion.
To get better control of the short exposures I was using with an arc lamp, I had to design and build a light integrator, using digital electronics techniques. This meter would first be adjusted for emulsion sensitivity, through tests, then a percentage of the full exposure time could be selected in 1% units from 1-99%. On reaching the set exposure, a buzzer would sound and the unit would turn off the light source. Either 110 or 220 volts could be selected to correspond with the power supplies I was using. While I had basically been able to solve the obstacle of retaining fine detail, ink was the major concern.
The problem that I immediately encountered was the inability to produce an edition using standard poster inks. The body of the inks and the rapid drying of the binder would limit me to about six prints before the fine detail would plug and dry-in. Washing the screen with an appropriate solvent would revive the screen for another six or so prints, but the continuous washing was more harmful to the screen than the action of the squeegee. Besides it was time consuming and an unpleasant dirty job. A better ink had to be found.
While presenting a paper on my toner tusche technique at the Tamarind Symposium in 1990, I asked the audience if there was a screen printer who would be interested in working with me on my upcoming sabbatical project and solve the ink drying puzzle. Jim Kraft of Albuquerque responded with some of his own tests and I went on my sabbatical to his shop to work with this master printer. His experience was very helpful and we soon developed a technique to retain the fine detail in toner washes and also found an oil based ink that allowed a continuous flow of prints.
Jim Kraft's Screenprint Shop
In his shop he used Ulano emulsion sensitized with diazo powder, and standard yellow monofilament fabrics with 300 - 355 threads per inch. A powerful mercury arc light with an integrator allowed for precise control of the very short exposure. While he used many good brands of opaque inks, he suggested a transparent base formulated for halftone work and colors mixed from the fine textured process colors. Twenty second exposures were found to be adequate and tests proved that the inks could print an entire edition without plugging the screen.
The nature of screen fabric is that only about 20% of the area is opened space when very fine material is used. For larger areas of color this presents no problem, but the single fine particles of toner must fall over the open area of the fabric if the ink is to pass through. Statistically this become an obstacle as the lighter tones are not reproduced linearly because the toner particle is much smaller than the individual strands of fibre and most would fall over them, rather than the opened spaces. The artist must adjust for this non-linear aspect of the reproduction of the toner drawing by producing a darker tint. Never-the-less, delicate washes were achieved that challenged those produced with lithography.
Because of the problems related with available waterbased inks, we did not try these materials, since his vast experience suggested the commercial materials would not come close to that achieved with the oil based products.
The Use of Toner for Tusche Wash Effects
Black toner particles are completely opaque which makes them a perfect medium for use directly in any photo-mechanical process. Depending on the composition of the toner material, it may be mixed with water, alcohol, hydrocarbon solvent and other solutions which can act as a carrier for the drawing (see my toner paper). Most toners now on the market can be "set" or bonded to the clear mylar with a simple solution of white gas from the hardware store. Others may require a small addition of a stronger solvent such as acetone or lacquer thinner to the white gas; or of a slow evaporating solvent like Varsol which will allow more time for the solvents to affect the toner particles. For more definite control over the way the toner settles on the mylar, one can also mix it with any glue like material that will bond to the clear plastic. Future Floor Polish, a clear acrylic polymer that is sold as a household kitchen floor polish, makes a very good carrier. This emulsion dries to a waterproof film that allows over-painting of the image. By adjusting the amount of water in the mixture, reticulation and brush marks can be controlled. Household ammonia can be used to remove dried unwanted areas. Methyl cellulose paste with a wetting agent dries to a different textured, very thin but more fragile film which can be easily scrapped off for close-cutting color areas etc.. I prefer clear mylar to the frosted plastic because shorter exposures are possible. Lines and solids can be made with any number of appropriate opaque materials that are common to the artists studio.
When using oil based inks one does not have to worry too much about the water resistance of the emulsion; many direct photosensitive emulsions can be given a short exposure and carefully developed. After drying, these will resist the action of the oil based inks and be adequate for printing the limited editions preferred by artists. Because some emulsions are not meant for waterbased inks, they will break down when used with these inks. While longer exposure may make them more water resistant, fine detail is destroyed.
Today the new dual cure emulsions are composed of a slow acting photosensitive plastic in place of non-sensitive polyvinyl materials, plus a diazo sensitizer that determines the exposure time of the image. After the screen is washed out and the image cleared, I give it a second exposure to harden the remaining plastic emulsion.
Coating the Screen
It is customary to apply 2 or more coats of emulsion to the screen to produce a tough stencil and reduce pin holes. I have found that only one coat is needed if care is taken in coating the screen. The emulsion should be as even as possible and that a scoop with a fairly sharp edge is used to produce the thin coating which gives this technique its particular quality. Using yellow monofilament screens with 305 and 355 threads per inch, I have never encountered many pin holes and the improved detail warrants this approach.
Today many schools and art printers are concerned about the health hazards encounters with solvents used in oil based inks. For that reason many schools have converted to the water based inks first designed for the textile industry. The binding medium used by the manufacturer will vary depending on the final product. Some, like Hunts Speedball, use acrylic based emulsions that leave a heavy layer of ink on T-shirt fabric, while others like Advance rely on dyes which can be set with heat. Other manufacturers take solvent inks and emulsify them so that they can be cleaned with water. In drying the prints, the toxic solvents are released into the studio. Again the fine artist must adapt to the available materials.
After trying these water based inks, I become convinced that none of the current materials would fulfill my needs. The colors were limited in scope and the fine detailed areas became plugged just like with the original oil based inks I had tried.
Tinted Transparent Bases are the Best Solution .
Because of the extremely fine detail that the dry copier toner produces, heavy pigmentation of the ink will produce problems in editioning. For this reason transparent bases, with their lack of particles, make a better ink. If the printer chooses to use oil based transparent base, then there are a number of options available for coloring. There are the magenta, yellow and cyan process colors that suppliers make for reproducing colored photographic images. These screen inks are extremely finely ground and can be used to mix all colors of the rainbow. Another solution is to use lithographic inks premixed in a small amount of transparent base; these pigments are very rich in color and little is needed to obtain the right saturation. Printers may also use the universal tinting colors which I also suggest for waterbased inks.
With waterbased inks one has to use pigments that have been ground in a carrier such as ethylene glycol which is miscible in both hydrocarbons and water. The major screen ink manufacturers supply a "toner" which is meant to alter the colors of their standard inks. These "toners" are very strong and are similar to the tinting colors one finds at the local paint store. The easy to obtain household tinting pigments are now made from azo or napthol dyes and are considered permanent for outdoor exposure and given a special rating for their lightfast characteristics. Considering that we see few new houses and cars which have faded under the sun, even with long exposures, we must look at these modern pigments as being adequate for fine art purposes. In a simple lightfast test, I had samples of screen prints half covered with black plastic starting in July. After 3 months of direct exposure to sunlight, I could see no bleaching of the household pigments, while a print using lithographic ink as colorant has shown lightening in the yellow and magenta pigments.
A Simple, Inexpensive Alternative Ink Base
The Japanese have for centuries used simple rice pastes to produce some of the most vibrant and permanent woodcut prints. With this in mind, I soon tried all available flours and starches which I cooked into a thick paste with the viscosity of screen inks. Some of the starches and flours could be made up into a perfect ink and I proceeded to print tests and even some editions from these simple transparent bases. I also used household paint tinting pigments to color the paste. Some of the pastes would work fine for smaller areas but would not allow the screen to release cleanly from the print if a large area was involved. This problem arises because of the very large structure of the starch molecule after it has absorbed water. The biggest problem with these pastes, especially those made from rice, was that they could not keep their viscosity for more than a few days and would become thin and watery. Bacterial disinfectants did not help this situation as the problem lays in the way starches become hydrolyzed when left in a completely wet state.
In Ralph Mayers' handbook I found a suggestion to use commercial wallpaper paste instead of preparing your own. The best of materials are used since most of these pastes are made either from inexpensive flour, starches or methyl cellulose. While some authors feel that these materials would not meet archival standards, others claim they would. I started to test the various wallpaper pastes that were available to me locally.
On the market there are both dry powder pastes and some that have been prepared ready for use. They may be made from wheat flour or some combination of flour and starches, or they may have methyl cellulose as the base. Methyl cellulose should be an ideal material as it would be compatible with the paper substrata. It is also non-shrinking and would have less effect on the curling of the finished print. Again the experts seem to disagree on the permanency of methyl cellulose, but I feel it should be every bit as enduring as the binders in litho inks, or the solvent based cellulose binder in poster screen inks. Unfortunately methyl cellulose also has a very large molecule when wet and this makes it hard to release the print from the screen when a large solid area is printed.
After trying a number of popular dry powder and ready prepared commercial wallpaper pastes, I found one that was far better than the rest, being near perfect as a ink base. Sold in Canada under the name of Dynamic Heavy Duty Wallpaper paste #210, this starch based clear buttery adhesive performed much better than the commercial waterbased inks. Tinted with paint toners and adjusted to the proper viscosity with a bit of methyl cellulose paste or plain water, it printed cleanly and was easy to wash up. If the ink was allowed to dry in the screen, a thick flood coat left to sit on the image for a minute or two is enough to soften the paste. A couple of proofs on newsprint leaves a clear image. By using methyl cellulose paste rather than just water to reduce the viscosity of the Dynamic paste, a greater bulk of ink was possible for a small investment. Lately, students have begun to use the paste direct from the container.
An 8.5 X 11 inch portion of a screen print, printed with water soluble paste.
The image was made with toner on mylar, exposed to direct coated emulsion.
A Waterproof Ink Base
If a water proof surface is really needed, I have found that Dynamic paste mixed with acrylic gloss media produced a good printing ink. If too much acrylic polymer is added to the cellulose, the screen could be hard to reclaim because of the water resistance of the acrylic film. Since my needs in screen printing is met with just the wallpaper paste, my experiments for a waterproof ink was not carried any further.
Printing the edition
A vacuum table and good urethane squeegees are helpful in producing the best possible prints. For accurate registration, pins and a paper punch are a must. With a good tight screen and modified Dynamic paste, editions that rival lithographs for delicacy of tints are possible.
Because this system is so sensitive to the screen image when it is printed in transparent colors, the condition of the squeegee becomes extremely important. A stiffer urethane blade is able to produce the finest tints but there must not be any roughness to the blade. Squeegees that have just been sharpened can have small particles of urethane partly torn away from the edge and these can produce a streaked print because the transparent colors began to show any difference in thickness of the application. I found that I had to polish the edge of a newly sharpened blade with a rag dipped in lacquer thinner. This slowly removed the fine protrusions and enabled me to get the perfectly even colored areas that I wanted.
Because paint manufacturers produce a very large amount of wallpaper paste to meet the needs of the industry, the unit cost of this material is very much less than for a gallon of traditional transparent base for the sign printer. Added to that is the saving over colored inks, which normally are priced 4-6 times the price of the tinted wallpaper paste. While the paint tinting colors can be very expensive for some of the new organic pigments, so little is required from these modern chemical marvels that their cost becomes minimal. If you can obtain a second hand pigment dispensing system like those at a paint store, accurate mixing of inks is an easy matter. Buy the lightfast exterior grade of pigments as they are not used in great quantity in any case. With the right choice of pigments, the colors that will be available is much brighter than from commercial screen inks.
When I tell artists about the printing medium used in some of my screen prints, I can see the look of horror for me using wallpaper paste and household tinting colors. Artists have been conditioned to use the best of materials to achieve permanent works of art and household products have rarely met the test in the past. The use of white acrylic household paint in place of acrylic gesso may not be a wise choice for painting, even though the acrylic polymer may have come from the same manufacturer. Additives to the basic formulation varies for the artists needs from those for the house painter. I have been in contact with the manufacturer of Dynamic paste and was told it is a corn starch product and has been tested only for adhesive qualities. They said it yellows slightly but could not give me a standard by which to judge. Considering that oil transparent bases also yellow, this at least should not be of concern for student work.
Because of the fine detail that this technique gives, printers cannot tell the difference between my screen prints and a lithograph. Screen prints usually consist of bold colors and hard-edged shapes; but toner can be used to give tusche like wash images. Graduated tints ranging from a whisper to dark passages are possible. I developed this technique not to make screen prints look like lithographs; but to give myself and other artists a method of getting delicate graduated tints that were not directly possible before in serigraphy.
Because of the availability of pastes and tinting colors at the local level, screen printing can now become an important factor in the art program of many rural schools. All that is needed is a stretched frame and a good squeegee for the student to produce art prints in a classroom, or posters for an upcoming school event. If these materials are as permanent as I believe, this technique should allow art printers greater flexibility and less environmental damage in producing their work.
Albert Kosloff, Photographic Screen Printing, ST Publications, Cincinnati, Ohio, 1987.
Nik Semenoff, Superior Tusche Washes, Leonardo, Volume 20, Number 1, 1987, pp71.
Dynamic Wallpaper Paste is manufactured by:
Evans Adhesive Corporation
925 Old Henderson Road
Columbus, Ohio. 43220
Ph. (614) 451-2666
It is made from corn starch, corn sugar and urea as main ingredients.
# 210 Dynamic Wallpaper paste is distributed through many local paint stores so check with those in your area.
Methyl cellulose can be obtained as a dry powder from the local wallpaper store, for an artists' quality, get yours from Daniel Smith in Seattle, Washington.
Points to Remember
1/ Use clear mylar for the greatest contrast and shortest exposure. The toner can be applied as a wash and set with white gas, or it can be mixed with an adhesive for a more controlled application.
2/ Keep the exposure as short as possible to retain the fine textures and tints. For a "posterized" effect for overprinting with a darker second screen, a longer exposure will tighten the image and give more modulation to the print. The new dual cure products are the best in my opinion.
3/ Do not use direct force from the hose when washing out the exposed emulsion. Use cold water and a gentle flow of water directed first on the frame of the screen. The newer direct emulsions are able to produce excellent results, even with some abuse of the image during washout.
4/ Other wallpaper paste product unknown to me may be as good or better than Dynamic. Do not thin the paste too much as bubbling on the printed surface could become a problem, as with commercial acrylic inks.
5/ If you are concerned with the lightfastness and permanency of household tinting pigments, Advance and TW sell "toners" which they claim are permanent. I am sure all of these type of colorants are ground in ethylene glycol compounds, which makes them miscible is both oil and water inks.
6/ Make sure your squeegee is fairly firm and has a smooth edge. Even a newly sharpen blade with have tiny ridges which will be reproduced in the transparent ink.
The author gives permission to photocopy this paper in the hope that toxic materials may be eliminated from the workshop. Publication without permission is prohibited